In a known compression-ignition internal combustion engine, such as a diesel engine, combustion takes place in one or more combustion chambers or cylinders. Air is compressed in the cylinder by a piston and fuel is injected into the compressed air. The heat of the compressed air spontaneously ignites the fuel in the cylinder.
In a common rail fuel delivery system, fuel is injected into the cylinders at high pressure, which is typically achieved using a high pressure pump to supply pressurised fuel to a common rail. In turn, the common rail is connected to a plurality of injectors, each of which is associated with one cylinder of the engine.
In conventional common rail fuel delivery systems the common rail fuel reservoir has an inlet and a plurality of outlets. A supply pipe connects the common rail inlet to the high pressure pump. Each of the plurality of common rail outlets delivers fuel to a respective fuel injector.
Each injector typically comprises a nozzle through which fuel is injected into the corresponding engine cylinder. The flow of fuel through the injector nozzle is controlled by a valve needle which is movable along a primary axis of the injector body and may be lifted from a valve seat adjacent to the nozzle in order to allow fuel to flow through the nozzle for injection into the cylinder.
A plurality of rail-to-injector connecting pipes are used to connect each outlet of the common rail to an inlet of the associated fuel injector. Accordingly, high pressure fuel in the common rail can be supplied to each fuel injector via its respective rail-to-injector connecting pipe.
The rail-to-injector pipes are typically formed from metal in order to withstand the forces exerted by the high pressure fuel flowing through them. Accordingly, the pipes are inflexible. Furthermore, the configuration of each pipe is constrained by the requirement to mitigate the effects of pressure waves propagating therethrough, during engine running. Such pressure waves are undesirable because they can adversely affect the amount of fuel injected during an injection event. Moreover, since the length and configuration of the pipe influences the propagation of pressure waves through it, a degree of uniformity of the pipe design is necessary such that each injector can be controlled according to the same injection strategy, i.e. typically all of the pipes are of equal length such that each one of the fuel injectors has the same pressure-wave characteristics. Additionally, there are constraints on the relative positions between the injectors, the rail and the pipes, which result from the design of the engine bay and the configuration of the engine block.
Due to the above-mentioned constraints, in conventional fuel delivery systems the pipes associated with adjacent fuel injectors overlap with one another such that, during maintenance or replacement of any one particular pipe, it is often necessary to first remove one or more of the other pipes. This increases the time taken for maintenance, and increases the chances of a pipe becoming contaminated with, for example, dust and dirt. Such contamination is highly undesirable since it may affect the flow of fuel to the injectors resulting in reduced engine performance and an increased possibility of engine failure.
It is an object of the present invention to substantially overcome or mitigate the above-mentioned problems associated with conventional fuel delivery systems.